Academic journal article The Science Teacher

Bigger Creatures Live Longer, Travel Farther

Academic journal article The Science Teacher

Bigger Creatures Live Longer, Travel Farther

Article excerpt

An enduring mystery in biology about the longer lifespans of bigger creatures may be explained by the application of the "Constructal Law," which states that anything that flows--a river, bloodstream, or highway net-work--will evolve toward the same basic configuration to be more efficient. This same basic law applies to all bodies in motion, be they animals or tanker trucks, says Adrian Bejan, the J.A. Jones Professor of mechanical engineering at Duke University and father of the Constructal Law.

In his latest theory paper, appearing in the journal Nature Scientific Reports, Bejan argues there is a universal tendency for larger things, animate and inanimate, to last longer and to travel farther. He starts his argument with an examination of the well-known observation in biology that larger animals tend to live longer. Bejan wanted to see if this general rule might apply to in-animate systems as well and proceeded to mathematically analyze the relationship in rivers, jets of air, and vehicles.

He found, as a general rule, that bigger rivers are older and that larger jets of air, such as atmospheric jet streams, last longer. By his calculations, larger vehicles should also last longer, but hard evidence of that is lacking, he says.

By being larger and lasting longer, all of these systems also travel farther, he says.

If you look at a moving vehicle or animal simply as a mass in motion, that is, something flowing, "the spreading of the mass of vehicles and animals is completely analogous to the flow of water in river channels," Bejan says. …

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